You went to a normal website and Safari slammed a full red-and-white warning in your face: "This Connection Is Not Private" — sometimes with a code like NET::ERR_CERT_DATE_INVALID or NET::ERR_CERT_AUTHORITY_INVALID. It looks like you got hacked. Almost always, you did not. This is your Mac refusing to trust a website’s security certificate, and the fix is usually 30 seconds of work.
Below is the fix-in-order list, safest first. Do them top to bottom and stop when the site loads.
First: is it one site or every site?
This one question tells you almost everything.
- One site only — the problem is that site’s certificate (expired, misconfigured) or your saved data for it. Low risk to your Mac.
- Every secure site — the problem is on your end: your clock, your network, a filter, or a security app. Start with the clock.
The fixes, fastest first
1. Check your date, time, and time zone — the #1 cause
Certificates are only valid inside a date range. If your Mac’s clock is wrong — even by a day, common after a dead battery or a long shutdown — every certificate looks "expired" or "not yet valid" and every HTTPS site breaks.
Open System Settings > General > Date & Time. Turn ON "Set time and date automatically." If it is already on, toggle it off and back on. Confirm the time zone is correct. Reload the page.
2. Reload, then try a Private window
A stale cached copy can trip the warning. Press ⌘R to hard-reload. Still stuck? Open a Private window (Shift-⌘-N in Safari, Shift-⌘-N in Chrome) and visit the site there. If it loads clean in Private, your saved cookies or cache for that site are the problem — see step 4.
3. Are you on public or hotel Wi-Fi? Log in first
Coffee-shop, airport, and hotel networks show a "captive portal" login page before they let you online. Until you accept it, your Mac cannot reach the real site and Safari shows a certificate error instead. Open a plain http site (like example.com) to force the login page to appear, sign in, then retry.
4. Clear this one site’s data (not everything)
In Safari > Settings > Privacy > Manage Website Data, search the site’s name, select it, and click Remove. This wipes only that site’s cookies and cache — you stay logged in everywhere else. Reload.
5. Restart your Mac and your router
The oldest fix that still works. A full restart clears a stuck network state and re-syncs the clock. If it is happening on every site, unplug your router for 30 seconds too.
6. Flush the DNS cache
A poisoned or stale DNS entry can send you to the wrong server, whose certificate will not match. In Terminal run: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder, enter your password, then reload.
7. Turn off any VPN, proxy, or content blocker
VPNs, corporate proxies, ad blockers, and "family safety" apps intercept HTTPS and can present a certificate your Mac does not trust. Disconnect the VPN and disable Safari extensions (Safari > Settings > Extensions) one at a time to find the culprit.
8. Update macOS
Certificate trust lives in macOS. An old, un-updated Mac eventually falls behind the current list of trusted authorities, so newer certificates read as untrusted. System Settings > General > Software Update and install what is offered.
When you should NOT click through
Safari usually offers a small "Show Details" and then a "visit this website" link. Ignore it in these cases:
- You are on public Wi-Fi and the warning is for a bank, email, or shopping login — someone could be intercepting the connection.
- The site is asking for a password or payment and you did not expect a warning here before.
- The certificate name in the details does not match the site you typed.
Bypassing the warning to reach a real, trusted site (after fixing your clock) is fine. Bypassing it to hand over a password on someone else’s network is not.
The honest part: when it is the Mac itself
If your clock will not hold the correct time after every restart, the small internal battery that keeps time may be failing — a repair, not a setting. And a Mac too old to run a current macOS will keep hitting certificate errors as the web moves on, because it can no longer receive the trust updates. If you are chasing this weekly on an older machine, it may be time to move on.
We sell certified refurbished Macs that run the latest macOS, so certificate trust just works — a MacBook Air (M1) starts at $450 and a MacBook Pro (M1 Pro) at $879, each with a warranty. Browse the Apple clearance collection for the current lineup, and if your old one still powers on, we will take it as a trade-in toward the upgrade.
Frequently Asked Questions
Does "This Connection Is Not Private" mean I have a virus?
No. It means your Mac could not verify the website’s security certificate. The most common cause is a wrong system clock, not malware.
Why does Chrome load the site but Safari shows the error?
Safari uses the macOS system trust store while Chrome keeps some of its own certificate settings, so a trust or extension issue can hit one browser and not the other. Fixing your clock and updating macOS resolves both.
It is only one website. Is that site dangerous?
Usually the site simply let its certificate expire or misconfigured it — annoying but not an attack on you. If it is your bank or a login page and you are on public Wi-Fi, do not proceed; use cellular data instead.
I fixed the clock and it still happens on every site.
Work down the list: restart, flush DNS, disable your VPN and content blockers, then update macOS. If it survives all of that on an older Mac, the machine may be too old to receive current certificate-trust updates.